Ohtsubo et al. (2014)

Ohtsubo, Y.(大坪庸介), Matsumura, A., Noda, C., Sawa, E., Yagi, A.(八木彩乃), &Yamaguchi, M.(山口真奈) (in press).
It’s the Attention That Counts: Interpersonal Attention Fosters Intimacy and Social Exchange.
Evolution and Human Behavior, 35(3), 237-244.
doi: 10.1016/j.evolhumbehav.2014.02.004
Human friendship poses an evolutionary puzzle, since people behave more generously toward their friends than the tit-for-tat strategy stipulates. A possible explanation is that people selectively behave in a generous manner toward their true friends, but not toward fair-weather friends. Social psychological studies have suggested that people use a partner’s attentiveness toward them as a cue to distinguish these two types of friends. Accordingly, it was hypothesized that people would increase their intimacy with a partner who was attentive to them. This hypothesis was tested by disentangling the frequent confounding between a partner’s attention and the benefits provided by the attentive partner in two scenario experiments (Studies 1a and 1b) and three laboratory experiments (Studies 2a to 2c). In Study 1, a partner’s attentiveness was manipulated independently of the benefit provided by the partner. In Study 2, the partner’s attention was experimentally dissociated from any potential benefit. These studies consistently showed that the participants increased their intimacy with a partner when they received attention from the partner. This result implies that models of the evolution of friendship must incorporate information exchange regarding the valuation of the relationship, as well as the exchange of fitness-related costs and benefits.